Effect of exchange and absorption potential in the distorted wave calculation of electron impact excitation of auto ionizing state of rubidium
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Date
2016-11
Authors
Agutu, Vincent Onyango Othieno Nunda
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Study of electron impact excitation of autoionizing states of alkali atoms is very important
because it can explain the additional peaks which appear in the ionization curve of the alkali
atoms. Very many researches have been made on the research of electron impact excitation of
autoionizing states of alkalis using close coupling method, R-matrix and Distorted Wave
Method. But in the Distorted Wave applied to electron impact excitation of rubidium atom only
the real potential i.e. static or static and exchange potential has been used. That is why in this
study complex distortion potential which includes static, exchange and absorption potential, has
been used for electron impact excitation of lowest autoionizing state of rubidium atom using a
distorted wave method. Initial and final state wave function of the projectile electron is distorted
by the complex potential. Differential and integral cross section and angular correlation
parameter have been calculated and compared with the available theoretical and experimental
results. Numerical calculations have been done using a modified dwbal fortran computer
program which was originally made for hydrogen atom. From the comparison of the results, it is
observed that in general the electron impact excitation cross section results are higher around
excitation threshold energy. This can be attributed to the exchange process which takes place in
the case of electron impact and also due to larger interaction between the projectile and the
target. It is also observed that the absorption potential lowers the cross section and brings it
closer to the experimental results. Alignment parameter results indicate that the integral cross
section results for m=O level are larger compared to m=1 level for impact energies up to about
400eV beyond which integral cross-sections for the magnetic sublevel m=1 become greater. The
lambda parameter indicates that more particles are scattered towards m=O for electron impact.
Description
A thesis submitted in partial fulfillment of the requirements for the award of the Degree of Master of Science in the School of Pure and Applied Sciences of Kenyatta University.
November 2016